Melittin-induced nociceptive responses are mediated by selective activation of capsaicin-sensitive primary afferent fibers and are modulated by excitatory amino acid receptor, cyclooxygenase, protein kinase C and serotonin receptor. The present study was undertaken to investigate the peripheral and spinal actions of voltage-gated calcium channel antagonists on melittin-induced nociceptive responses. Changes in mechanical threshold and number of flinchings were measured after intraplantar (i.pl.) injection of melittin (30microg/paw) into mid-plantar area of hindpaw. L-type calcium channel antagonists, verapamil [intrathecal (i.t.), 6 or 12microg; i.pl.,100 & 200microg; i.p., 10 or 30 mg], N-type calcium channel blocker, omega-conotoxin GVIA (i.t., 0.1 or 0.5microg; i.pl., 5microg) and P-type calcium channel antagonist, omega-agatoxin IVA (i.t., 0.5microg; i.pl., 5microg) were administered 20 min before or 60 min after i.pl. injection of melittin. Intraplantar pre-treatment and i.t. pre- or post-treatment of verapamil and omega-conotoxin GVIA dose-dependently attenuated the reduction of mechanical threshold, and melittin-induced flinchings were inhibited by i.pl. or i.t. pre-treatment of both antagonists. P-type calcium channel blocker, omega-agatoxin IVA, had significant inhibitory action on flinching behaviors, but had a limited effect on melittin-induced decrease in mechanical threshold. These experimental findings suggest that verapamil and omega-conotoxin GVIA can inhibit the development and maintenance of melittin-induced nociceptive responses.
Animals ; Calcium Channels* ; Calcium Channels, L-Type ; Calcium Channels, N-Type ; Calcium Channels, P-Type ; Calcium* ; Hyperalgesia ; Ions* ; Melitten ; Nociception* ; omega-Agatoxin IVA ; omega-Conotoxin GVIA ; Prostaglandin-Endoperoxide Synthases ; Protein Kinase C ; Rats* ; Receptors, Glutamate ; Serotonin ; Verapamil

Hepatic stellate cells (HSCs) play a key role in liver fibrosis. Succinate and succinate receptor (GPR91) signaling pathway are involved in the activation, proliferation, and migration of HSCs. We investigated whether succinate may induce hepatic fibrosis. The mice were randomly divided into 2 groups —the control group (chow diet-fed mice, n = 26) and sodium succinate group (2% sodium succinate + chow diet, n = 38). Each diet was provided for 16 weeks. Mice administered an oral diet of 2% sodium succinate for sixteen weeks lost body weight and had increased serum alanine transaminase and hepatic triglyceride contents compared to those in the control mice. Moreover, mice fed with sodium succinate showed increased expression of the alpha smooth muscle actin protein and gene in the liver at 8 weeks of feeding and increased fibrosis in their histology at 16 weeks of feeding. However, the expression of the GPR91 protein and mRNA increased at 4 weeks of feeding, but decreased at 8 and 16 weeks of feeding. These results suggest that an oral succinate diet could induce liver damage and liver fibrosis in mice and that GPR91 signaling might be an early marker or sensor of hepatic fibrosis development.

Background: Hepatic stellate cells (HSCs) are the major cells which play a pivotal role in liver fibrosis. During injury, extracellular stimulators can induce HSCs transdifferentiated into active form. Phloretin showed its ability to protect the liver from injury, so in this research we would like to investigate the effect of phloretin on succinate-induced HSCs activation in vitro and liver fibrosis in vivo study. Methods: In in vitro, succinate was used to induce HSCs activation, and then the effect of phloretin on activated HSCs was examined. In in vivo, succinate was used to generated liver fibrosis in mouse and phloretin co-treated to check its protection on the liver. Results: Phloretin can reduce the increase of fibrogenic markers and inhibits the proliferation, migration, and contraction caused by succinate in in vitro experiments. Moreover, an upregulation of proteins associated with aerobic glycolysis occurred during the activation of HSCs, which was attenuated by phloretin treatment. In in vivo experiments, intraperitoneal injection of phloretin decreased expression of fibrotic and glycolytic markers in the livers of mice with sodium succinate diet-induced liver fibrosis. These results suggest that aerobic glycolysis plays critical role in activation of HSCs and succinate can induce liver fibrosis in mice, whereas phloretin has therapeutic potential for treating hepatic fibrosis. Conclusion Intraperitoneal injection of phloretin attenuated succinate-induced hepatic fibrosis and alleviates the succinate-induced HSCs activation.

Objective: To investigate the effects of a herb complex extract (HCE) prepared from Cornus officinalis Sieb. Et Zucc., Eriobotrya japonica Lindley, and olive leaves on immune response of mouse spleen NK cells in vitro and in vivo analysis. Methods: The activity of natural killer (NK) cells was measured in splenocytes and YAC-1 cells. Mice were immunosuppressed using cyclophosphamide (5 mg/kg body weight). Three different doses of HCE (200, 400, and 800 mg/kg body weight) and red ginseng extract (800 mg/kg body weight) which was used as standard immunomodulatory herb were administered orally for 4 weeks. The body weight, dietary, water intake, organs (liver, thymus, and spleen) weight, completed blood count, and cytokines (tumor necrosis factor alpha, interferon gamma, and interleukin-2) production was measured. Results: At the maximum concentration of HCE, the activity of NK cells was increased by 48.5%. HCE increased liver, spleen, and thymus weights without altering numbers of white blood cells, lymphocytes, and neutrophils in a cyclophosphamide-induced immunosuppression rat model. However, HCE recovered the inhibited cytokine expression; HCE (800 mg/kg) increased cytokines levels. The results indicate the immune enhancement potential of this HCE. Conclusion: The HCE enhances immunity by increasing NK cell activity, regulating cytokine levels, and maintaining spleen weight. Therefore, it may be used as a potential immunity enhancer.